The absorption of dietary oxalate makes a significant contribution to the amount of oxalate excreted in urine and thus plays an important role in the development of calcium oxalate kidney stones. Current therapies to limit this risk factor are low oxalate diets and dietary supplementation with calcium. These approaches are only partially effective and a more efficacious therapy is required. Removal of oxalate from ingested foods by digestion is the approach to be evaluated in this research proposal. The efficiencies of oxalate degrading enzymes and oxalate -degrading bacteria in digesting the bioavailable oxalate in spinach and bread will be investigated in vitro. The bacteria used will be Oxalobacter formigenes, a normal part of the colonic flora in humans that uses oxalate as its sole source of carbon. The enzymes examined will include oxalate oxidase, an O2-requiring enzyme isolated from sugar beet, and the oxalate degrading enzymes from Oxalobacter formigenes, which do not require O2. The efficiency of these systems in degrading oxalate, singly or in combination will be evaluated using capillary electrophoresis and a method developed for measuring food oxalate. PROPOSED COMMERCIAL APPLICATION: Urolithiasis is a common disease with a few therapies that are effective in eliminating recurrences in susceptible individuals. This there is a large market for a product that can reduce urinary oxalate excretion that could potentially benefit all calcium oxalate stone formers. The proposed therapy would be a supplement to be taken with meals that digested oxalate before it could be absorbed.